The present invention relates to a polyarylene sulfide resin composition. More particularly, the present invention relates to a polyarylene sulfide resin composition having an improved crystallization speed and excellent heat resistance and moldability.
Frame-retardant thermoplastic resins having high heat resistance and high chemical resistance are required as materials of construction for components in electric and electronic applicances, automobile appliances and chemical instruments. A polyarylene sulfide resin (PAS) represented by polyphenylene sulfide (PPS) is one of the resins satisfying this requirement and the demand for such a resin is increasing because it can afford superior physical properties with a relatively reduced cost.
However, when PAS is processed by injection molding, the resin takes on a peculiar crystallization behavior and many undesirable phenomena are observed in the molding operation.
Further, since the crystallization speed of PAS is low, a molded article of high crystallinity cannot be obtained unless molding is carried out at a high mold temperature.
The following techniques of accelerating the crystallization of PAS have been recently proposed.
(1) An oligomeric ester is added (see Japanese Patent-Laid-Open No. 45654/1987).
(2) Another thioether is added (see Japanese Patent Laid-Open No. 230849/1987).
(3) A carboxylic acid ester is added (see Japanese Patent Laid-Open No. 230848/1987).
(4) A certain phosphoric ester is added (see Japanese Patent Laid-Open No. 230850/1987).
Unfortunately, these methods have been found to yield the following problems. Namely the heat resistance of the additive is poor and an evaporation gas or decomposition gas is generated during molding.
Furthermore, if the molded piece is annealed, the additive is diffused to cause weight reduction.
Accordingly, an object of the present invention is to develope a polyarylene sulfide resin composition, especially a polyphenylene sulfide resin composition, having an increased crystallization speed sufficient to forgo the necessity of using a high mold temperature in injection molding.
Another object of this invention is to provide a polyarylene sulfide composition having a high crystallinity even if molding is carried out at a low mold temperature.
Still another object of the invention is to provide a polarylene sulfide composition which does not generate either an evaporation or decomposition gas during extrusion or molding.